A term for a feature of Western neumatic notation. Liquescence arises in singing diphthongs and certain consonants to provide for a semi-vocalization of that vowel or consonant as a passing note to the next pitch. It is indicated by special neume shapes in all the regional notations of Western chant. Mocquereau listed the following situations where liquescence occurs: on the consonants l, m, n, r, d, t and s, when these are succeeded by another consonant; on the double consonant gn; on i and j, when these follow another consonant; on m and g, when these have a vowel on either side; and on the diphthongs au, ei and eu. Liquescent neumes include the following, in which it is understood that the last note of each neume is semi-vocalized: the Epiphonus, two notes in ascending order, the liquescent podatus (see Pes (ii)); the Cephalicus, two notes in descending order, the liquescent Clivis; and the Ancus, three notes in descending order, the liquescent Climacus. (For illustrations see Notation, Table 1; Bannister and Suñol contain illustrations of liquescent neumes in the notations of different regions.)
A. Mocquereau: ‘Neumes-accents liquescents ou semi-vocaux’, Le répons-graduel Justus ut Palma, PalMus, 1st ser., ii (1891), 37–86
C. Vivell: ‘Liqueszierende Choralnoten’, Gregorianische Rundschau, iv (1905), 65
R. Baralli: ‘Le figure dell’“Ancus” o “Climacus liquescens” nei manoscritti gregoriani, loro significato ed esecuzione’, Rassegna gregoriana, vii (1908), cols.401–10, 481–98
H.M. Bannister: Monumenti vaticani di paleografia musicale latina (Leipzig, 1913/R)
G.M. Suñol: Introducció a la paleografia musical gregoriana (Montserrat, 1925; Fr. trans., rev., enlarged 2/1935)
H. Freistedt: Die liqueszierenden Noten des gregorianischen Chorals: ein Beitrag zur Notationskunde (Fribourg, 1929)
J.B. Göschl: Semiologische Untersuchungen zum Phänomen der gregorianischen Liqueszenz: der isolierte dreistufige Epiphonus praepunctis, ein Sonderproblem der Liqueszenzforschung (Vienna, 1980)
D. Hiley: ‘The Plica and Liquescence’, Gordon Athol Anderson, 1929–1981, in memoriam, ed. L.A. Dittmer (Henryville, PA, 1984), 379–92
A. Haug: ‘Zur Interpretation der Liqueszenzneumen’, AMw, l (1993), 85–100